Dynamo construction.



HENRY LEITNER, OF WOKING, ENGLAND.

DYNAMO CONSTRUCTION.

Specification of Letters Patent.

Patented July 23, 1907.

Application filed August 9,1905. Serial No. 2'73A03.

To all whom it may concern:

Be it known that I, IIENRY Linrivnn, a subject of the King of Great Britain, residing at Maybury, \Voking, Surrey, England, have invented new and useful Improvements in Dynamo Construction, 01' which the following is a specific-mien.

The present invention refers to means for regulating direct current dynamos so as to render their output constant Within certain limits in spite of any variations of the speed at which they. may be driven. A machine regulated in such a manner is specially suited to the electric lighting of railway trains when mounted underneath the carriages to be lighted and driven by a belt or other convenient means from the axle ol the said carriage a battery of accumulators being used in combination therewith in the usual and well known manner.

It will be understood that the principles of the invention may be readily applied to any multipolar direct current dynamo, but for the sake of simplicity I and to enable the principles involved to be .the more readily understood it will be described with reference to a two pole machine.

The general principle which is employed in carry ing the invention into practical effect is to make use of subsidiary poles arranged between those poles of the machine which are excited irom the main brushes and which will be accordingly referred to as the main poles oi the machine these subsidiary poles being excited by a field winding supplied from additional brushes arranged to make con tact with the commutator.

A secoi'idary important feature is that the machine will excite to furnish current in the same sense or direction no matter in which direction the armature may be driven.

In order that my invention may be more fully understood, I will describe the same by reference to the accompanying drawings, in which:-

a is the armature, b and b the brushes from which the main current generated in the machine is taken oil.

0, c are the brushes which provide current for exciting the so-called subsidiary poles (l, d referred to above and these brushes 0, c are connected to the field winding c, c which excites the said subsidiary poles.

The main poles f, f of the machine are provided with an ordinary shunt field winding g, g connected to the main brushes I), f in the manner shown.

It is to be understood that the tour brushes of the machine must be arranged in the position shown that is to say approximately in the center of each of the polar spans.

It is of course understood that in speaking of the po sition of the brushes it is assumed that the commutator bars from which the brushes collect are in line with the windings to which they are attached, asl'or example is usual in a Gramme ring. Where there is an angular displacement between the commutator bars and their corresponding windings the brushes obviously must be correspondingly displaced. it must also be understood that the so-called main poles of the machine must be possessed of residual magnetism and the magnetism of these poles however it may change in strength remains unreversed, whereas the magnet ism of the so-called subsidiary poles changes in sign according to the direction of rotation of the armature, and the subsidiary poles should accordingly be of soft iron and laminated throughout. 7

The function of the machine is as followsz-Supposing the armature a to be rotated clockwise the residual magnetism in the poles f, f produces a P. D. between the brushes 0, c which immediatelycauses a current to flow in the field-windings e, a of the subsidiary poles d, d exciting these latter in such a sense that their action upon the armature a produces a P. D. between the main brushes 1), b with the result that the field windings g, g of the main poles f, f receive current in such a sense as to increase their residual magnetism.

The increased magnetic flux of the main poles f, f acting upon the armature a increases the current dclivered by the brushes 0, c to the field windings e, c of the subsidiary poles d, d and these interactions continue to increase till the P. D. of the main brushes b, b exceeds that of the battery of accumulators it is arranged to charge and operates the usual automatic cutin and cut-out switch which establishes connection between the brushes b, Ii and the battery. As soon as the brushes 1), b commence to deliver current to the external circuit, armature reactions are set up which markedly weaken the effective magnetism of the main poles f, f and in consequence the exciting current flowing in the hold windings e, e of the subsidiary poles d, d and therefore in turn the current furnished by the brushes b, b, the exciting current for the field windings g, 9 derived from it being likewise proportionately weakened. It is therefore plain that the ar-, rangements described have the result of utilizing the armature reaction caused by the production of useful current, to regulate automatically in a cumulative sense against any appreciable increase in the external or useful current in excess of the predeterminedamount for which the machine has been designed or adjusted, whatever causes may conduce thereto, such as increased speed of rotation. The machine is therefore a machine the output of which within very wide limits does not increase with speed. When the machine is rotated in the opposite or anticlockwise ,direction it is manifest that the socalled subsidiary poles (l, d are excited in the reverse sense and therefore change their polarity. As the direction of rotation is at the same' time reversed the direction of current furnished by the main brushes Z1, I) remains the same, and consequently the polarity of the main poles is unatl'eeted and the whole series of interaetions oeeut' as previously deseribed in referenee to rotation in the eloekwise direction.

The purely magnetie et't'oet ot' the so-ealled subsidiary polepieees (I, d on the main pole pieces/1] may be deseribed as disloeatine the held of the pole pieces f, f so that it is drawn t wards the subsidiary pole pieees (I, d ina direction opposed to the direction of ro tation, (and tints P. D. is produced between the main brushes [1, I) as affected by the polesf,f) whereas the armature reaction produeed by the external current supplied from the brushes (i, I) opposes this dislocation by its tendeney to distort the held in the direction of rotation proportionateiy to eurrent and speed. ,But this distortion in bring-in the so-ealled main poles towards their normal position diminishes the l. 1). across the brushes 1), b and theret'ore the output of the maehine, and thus a condition oi balanee is produced which counteracts any tendent'y to increase of output with int-reusing speed.

It will be obvious that the presence of commencing magnetization in the polesf may be insured either by taking the current for the lamps the maehine is designed to supply through an additional exciting wind- 1 ing in the known manner or by making the magnets Wholly or partially ot' sullieiently hard materiaL For purposes oi better adjustment a differential or reverse Compound winding may he employed on the poles/,f. that is to say, the main eurrent t'romtheinain l l l i l l t l t brushes 1), b is taken round the poles/.f in a direetion weakening the same.

Having now partieularly deseribed and aseertained the nature of my said invention and in what manner the same is to be performed, I deelare that what .I elaini is:

1. A dynamo havingtield magnets in a shunt: of the main eireuit. and being also provided with subsidiary magnets having poles distinet and separate from the poles of the field magnets. and with tixed subsidiary brushes t'on neeted with the euils oi the subsidiary magnets. substau tiall as deseribed.

L. in a dynamo. the eombination with the tield magnets, armature and main line brushes. the rolls oi said magnets beingin a shunt ot' the main line. of subsidiary magnets forming a subsidiary tield and tixed subsidiary brushes eonneeted to and supplying eurrent; to the eoils oi the sub sidiary magnets. substantially as described.

It. in a dynamo the eotnbiinttion with an armature. main line brushes and tield magnets in a shunt ol the main eireuit. of subsidiary magnets having their poles in a plane interset'tint: the plane of the poles of the main may nets and subsidiary brushes eonueeted to the eoils ot' the subsidiary magnets, substantially as deseribed.

4. in a dynamo. the. combination with an armature.

main line brushes and tield magnets in a shttnt ot' the tuain eireuit. subsidiary magnets having their poles loeuted in a plane interseeting the plane of the poles ot' the main maenets and subsidiary brushes rennet-ted with the rolls oi the subsidiary magnets. the brushes beinu, located in a line bi seetine' the poles of their magnets. substantially as de seribed.

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